ZrO in Class M Stars

Twenty ZrO bands have been found in the spectrum of fi Pegasi (M2). All the stronger members of the system y have been identified. Seven bands could not be iden- tified with any other element or compound. The rest are blended with atomic lines, but the presence of the bands can hardly be doubted. The behavior of the strongest ZrO band at X 6473.7 has been studied in the brighter stars of class M. It is found to be especially strong in j3 Pegasi and p Persei. It is shown that the behavior of the ZrO band cannot be explained by the variation of either tem- perature or pressure. The most likely explanation is the unusual abundance of ZrO in the atmospheres of these two stars